I’ve not had mine powder coated, but I have put a different set of wheels on my car (VW Motorsports in anthracite), and they’re powder coated. I really dislike diamond cut alloys because of the poor durability of the diamond cut finish. They have a ‘blingy’ showroom appeal, but are really not suited to the sort of weather we get in the UK in winter. I wish that VW would offer a powder coated alloy as an option on the GTI; I’d pick a powder coated wheel over a diamond cut one every time.
I’m a member on the Golf forum that you’ve posted the link to, and I remember seeing the pictures of those Santiago alloys (in fact, mine is the first reply to that post!). IMO they look so much nicer with a powder coated finish than they did when they were diamond cut.
On my previous car (mk6 Golf), two of the diamond cut wheels succumbed to white worm corrosion, in spite of the wheels being washed every week to ten days, and always being well protected with sealant and wax, and any stone chips on the diamond cut areas being touched in with clear lacquer pretty much as soon as it occurred. VW replaced those wheels under warranty.
Is your car is under 3 years old? I’m assuming it is as it’s a 6c GTI and I seem to remember the first 6c GTI’s came into the UK around March/April 2015. If it is still under warranty, it’s worth trying to get them replaced under warranty. A word of caution; if they show other signs of damage (other than the white worm), VW are unlikely to entertain a warranty claim. I suppose the only issue with getting your existing wheels powder coated is that when you come to sell it, if you part exchange it against another VW, the dealer may knock the p/ex value down because the wheels no longer have the original finish.
The diamond cut alloys will be going back on when I eventually sell the car, and if I get another Polo and it has diamond cut wheels, the Motorsports will be going straight on; assuming the bolt pattern and centre bore of the new Polo is the same as the 6c model.
Here’s my GTI with powder coated alloys on;
